Thanks for the advice. I have tried vallis unsuccessfully hence the cry for helpWell, plants dont really care about pH but...
I reckon Crypt Balansae would do ok. I was going to suggest vallis but it's harder to keep vallis in softwater conditions.
Hygrophila polysperma never fails
Aponogeton crispus 'Red' and Echinodorus uruguayensis are worth a look too.